Friday, April 29, 2016
Late spring frost damages flowers and young leaves!
Posted by Amanda Gallinat
One feature of climate change that's of interest to our lab is the increasing likelihood of frost damage to flowers and young leaves in the spring. Warm temperatures cause plants to flower and leaf-out earlier, and increasing variability in spring temperatures, including late-spring frost events, is leading to a greater likelihood that vulnerable flowers and young leaves will be damaged by frost. This spring, we have seen this phenomenon in action in the Boston area!
Following a record-breaking warm winter and warm spring, plants at the Arnold Arboretum started leafing out and flowering at the end of February!
These photos of Hamamelis mollis (top left), Lonicera korolkowii (top right), Lonicera tatarica (bottom left), and Cornus officinalis (bottom right) were taken at the Arboretum on February 28, 2016.
In early April (4-6), after several hundred species of plants had leafed out and/or flowered at the Arboretum, freezing nighttime temperatures (between 22 and 25 degrees F) hit the Boston area. The results varied among species in the days and weeks that followed. Some species' flowers and flower buds never recovered, and this was particularly striking in the collection of cherry trees at the Arboretum:
Sargent's cherry (Prunus sargentii) during peak flowering in 2015 (left) and 2016 (right). The inset photo shows heavy frost damage to flower buds and light frost damage to young leaves.
Other plants like Forsythia sp. had flowers that were also badly damaged by frost. For wild plants, frost damage to flowers can have dramatic consequences for reproduction.
Forsythia flowers at the Arboretum, typically healthy and bright yellow, are now mostly drooping and golden-brown
In addition to frost damage to flowers and flower buds, we observed that many young leaves were killed or damaged by the frost. We have recently conducted experiments on the frost tolerance of young leaves in the laboratory, so we were particularly interested in seeing the effects of a natural frost on leaves at the Arboretum. In some cases, such as many of the Berberis species, leaves showed almost no damage following the natural frost. In other species, leaves that looked heavily damaged in the days following frost events were able to mostly recover, such as in Prinsepia sinensis, while some species appear to have sustained permanent frost damage. It is unclear whether heavily damaged plants will re-flush new leaves or simply undergo limited photosynthesis during this growing season.
Prinsepia sinensis just after a frost (April 5th, left) and a few days later (April 7th, right)
If you are in the Boston area or your region also experienced a late spring frost, we encourage you to look for signs of frost damage to flowers and leaves!
Frost damage is clearly visible on the flowers of this Magnolia stellata